Polar solvent-based drilling fluids include water, ethylene glycol, propylene glycol, glycerol, N-methylpyrrolidone, and other solvents that are water soluble or miscible. Drilling muds can contain an oil soluble polymer in the form of a gel as fluid loss reducer. A process for preparing an oil soluble polymer fluid loss control agent may include the steps of dissolving at least one polymer in a hydrocarbon oil to form a clear solution or a gel, adding an emulsifier to the solution or the gel, and keeping the mixture under conditions of agitation until a clear creamy mixture is obtained. Because of high temperature stability of the polymer used, this fluid loss agent can be used at high temperature and high pressure in water-based muds.
The use of oil soluble polymers with surfactants is distinct from using polymers made with hydrophobic and hydrophilic monomers. Usually oil soluble polymers/hydrophobic polymers have higher temperature stability than water soluble polymers/hydrophilic polymers. However, the present invention offers thermal stability of hydrophobic polymers while using hydrophilic polymers to help disperse the hydrophobic polymer in water instead of using surfactant.